Energy Ray-Curable Polymer, an Energy Ray-Curable Adhesive Composition, an Adhesive Sheet and a Processing Method of a Semiconductor Wafer

ABSTRACT

In a pressure-sensitive adhesive composition or a pressure-sensitive adhesive sheet containing an energy ray-curable polymer, problems associated with the volatilization of a low molecular weight compound contained in the composition are overcome. An energy ray-curable polymer characterized by comprising a radical generating group, which is capable of initiating a polymerization reaction upon excitation with an energy ray, and an energy ray-polymerizable group bonded together in the main or side chain.

This application is a Continuation Application of U.S. Ser. No.12/935,677, filed on Dec. 6, 2010, which is a U.S. national stageapplication of PCT/JP2009/054742 filed on Mar. 12, 2009, which claimspriority of Japanese patent document 2008-093897 filed on Mar. 31, 2008in Japan, the entireties of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an energy ray-curable polymer, anadhesive composition and the adhesive sheet using thereof. Also, thepresent invention relates to the processing method of the semiconductorwafer, and in particular the present invention relates to a backsideprocessing of the semiconductor wafer and the dicing processing of thesemiconductor wafer.

BACKGROUND OF THE INVENTION

After a circuit is formed on the surface of the semiconductor wafer, agrinding processing is performed to the backside of the wafer, thebackside grinding step which controls the thickness of the wafer and thedicing step which separate the wafer into predetermined chip size arecarried out. Also, followed by the backside grinding step, theprocessing treatment which involves a heat generation such as an etchingtreatment is further performed to the backside.

During the etching of the backside grinding, the adhesive sheet socalled backgrind tape is stuck to the circuit surface of the wafer inorder to protect the circuit. Also, during the dicing of the wafer, theadhesive sheet so called a dicing tape is stuck to the backside of thewafer in order to prevent the scattering of the chips which are formedby dicing (hereinafter, such adhesive sheet in total may be described as“a semiconductor wafer processing adhesive sheet” or “a wafer processingadhesive sheet”.

As for these wafer processing adhesive sheet, in particular as for thebackgrind tape, it is required,

-   to prevent the damage to the circuit and the wafer body,-   to have no residue of the adhesive agent (glue residue) of the    adhesive agent on the circuit after the releasing,-   to prevent the penetration of the grinding water to the circuit    surface which washes out the grinding debris generated during the    backside grinding and removes the heat generated during the    grinding, and-   to sufficiently maintain the precision of the wafer thickness after    the grinding.

Further, when performing the processing treatment involving a generationof the heat or a heat application to the backside, it is required thatthe volatile component is not generated from the adhesive layer.

Also, as for the dicing tape, it is required,

-   to hold the wafer with a sufficient adhesive force during the    dicing,-   to release the chip easily from the dicing tape during the pickup of    the chip,-   to have no reside of the adhesice agent on the backside of the chip    which is picked up, and-   that the low molecular weight composition which is included in the    adhesive layer does not flow out due to the dicing water during the    dicing.

As for such wafer processing adhesive sheet, the adhesive sheet iswidely used which is provided with the energy ray-curable adhesivelayer, which cures by the energy ray such as ultraviolet ray, on thesubstrate consisting of the resin film. According to the adhesive sheetof the energy ray-curable type, during the backside grinding or dicingof the wafer, the wafer is held by strong adhesive force; therefore thegrinding water is prevented from penetrating into the circuit surfaceand the chip is prevented from scattering. Also, after finishing thebackside grinding or the dicing, the adhesive force is reduced since theadhesive layer cures by irradiating the energy ray thereto, hence thewafer (chip) is released from the adhesive sheet without the glueresidue.

As for the energy ray-curable adhesive agent, the adhesive agent formedby blending the energy ray-curable resin having relatively low molecularweight and the photo polymerization initiator to the acrylic adhesivepolymer, is well known. However, as for such adhesive agent, because itincludes the low molecular weight substances each component is notnecessarily mixed uniformly, and when the energy ray curing is carriedout, an insufficient curing of the adhesive agent occurred in somecases, or the low molecular weight substances remained unreacted in somecases. Therefore, the adhesive agent remained on the wafer (chip) insome cases, or the wafer (chip) was contaminated by the low molecularweight substances in some cases.

In order to resolve such problems, the wafer processing adhesive sheetis proposed which comprises the energy ray-curable adhesive layercomprising the photo polymerization initiator and the energyray-polymerizable adhesive polymer (hereinafter, it may be described as“polymerizable group adduct type adhesive agent”) introducing the energyray-polymerizable group in the molecule of the adhesive polymer byreacting the acrylic adhesive polymer to the compound including theenergy ray-polymerizable group (Patent document 1). According to suchpolymerizable adduct type adhesive agent, the polymerizalbe group isuniformly dispersed in the adhesive layer, and the contamination due tothe insufficient curing or the low molecular weight substances isreduced since the low molecular weight substances low.

Similarly, the polymer is proposed which binds the group forming thefree radical which initiates the polymerization reaction under theexcitation by the energy ray to the adhesive polymer (Patent document2), or the polymer binding the photo polymerization initiator to theadhesive polymer is proposed (Patent document 3) in order to prevent theinsufficient curing of the adhesive agent after the energy rayirradiation (hereinafter, these may be described as “radical generatinggroup adduct type adhesive agent”). These radical generating groupadduct type adhesive agent does not have polymerizing property byitself, therefore it is used together with the energy ray-curable resinhaving relatively low molecular weight substances as described in theabove.

-   Patent document 1: JP-A-H09-298173-   Patent document 2: JP-A-H08-333555-   Patent document 3: JP-A-H09-111200

DISCLOSURE OF THE INVENTION Technical Problems to be Solved by theInvention

As for the energy ray-curable adhesive agent using the polymerizablegroup adduct type adhesive agent described in the above, the photopolymerization initiator is blended together with the polymerizablegroup adduct type adhesive agent. Also, the radical generating groupadduct type adhesive agent of the patent document 2 and 3 is usedtogether with the energy ray-curable resin. Both the photopolymerization initiator and the energy ray-curable resin are compoundshaving relatively low molecular weight.

The energy ray-curable adhesive layer is obtained by diluting the abovementioned solvent followed by applying to the substrate or the releasefilm then drying. However, in case the low molecular weight compound isincluded in the energy ray-curable adhesive agent, the low molecularweight compound volatilizes during the drying; hence the adhesive agenthaving the composition as designed couldn't be obtained in some cases.

For example, when using the photo polymerization initiator having lowmolecular weight, the photo polymerization initiator is volatilizingduring the drying. If this happens excessively, then curing of theadhesive agent by the energy ray irradiation becomes insufficient;thereby there are problems that it causes the adhesive force after thecuring to rise and also causes the glue residue against the adherend.

Also, when performing the wafer processing by using the wafer processingadhesive sheet, in case of performing the heat treatment to thesemiconductor wafer or in case of carrying out the processing involvingthe heat application or heat generation as dry etching, the processingmay be carried out under reduced pressure or in vacuo. Here, the lowmolecular weight compound remained in the adhesive layer after thecuring volatilizes and causes similar problem as mentioned in above orit may contaminate the semiconductor apparatus due to the volatile gascomponent generated.

Furthermore, when using for the wafer processing, the water is sprayedin order to remove the heat and the cutting debris generated during thewafer backside grinding or the dicing. Here, the low molecular weightcompound included in the adhesive layer may flow out.

Therefore, in regards with the energy ray-curable adhesive compositionused in the wafer processing adhesive sheet, the present invention aimsto solve the various problems accompanied with volatilization of the lowmolecular weight compound included in the composition.

Means for Solving the Problems

The objectives of the present invention aiming to solve such problemsare as follows.

(1) An energy ray-curable polymer having a radical generating groupcapable of initiating polymerization reaction under the excitation by anenergy ray, and an energy ray-polymerizable group bonded to a main chainor a side chain of the polymer.

(2) The energy ray-curable polymer as set forth in (1) wherein saidradical generating group includes a phenyl carbonyl group which maycomprise a substituent group in an aromatic ring.

(3) The energy ray-curable polymer as set forth in (1) or (2) whereinsaid radical generating group is derived from a monomer obtained byadding a compound comprising a polymerizable double bond to a hydroxylgroup of a photo polymerization initiator comprising hydroxyl group.

(4) The energy ray-curable polymer as set forth in any one of (1) to (3)having a weight average molecular weight of 300,000 to 1,600,000.

(5) An energy ray-curable adhesive composition comprising the energyray-curable polymer as set forth in any one of (1) to (4).

(6) An adhesive sheet comprising a substrate and an energy ray-curableadhesive layer formed thereon, and said energy ray-curable adhesivelayer comprising the energy ray-curable adhesive composition as setforth in (5).

(7) The adhesive sheet as set forth in (6) used for a semiconductorwafer processing.

(8) A processing method of a semiconductor wafer comprising the step ofadhering the energy ray-curable adhesive layer of the adhesive sheet asset forth in (7) to a circuit surface of the semiconductor wafer formedwith the circuit on the front surface, and performing the backsideprocessing of the wafer.

(9) The processing method of the semiconductor wafer as set forth in (8)wherein said backside processing of the semiconductor wafer is thebackside grinding.

(10) The processing method of the semiconductor wafer comprising thestep of adhering the energy ray-curable adhesive layer of the adhesivesheet as set forth in (7) to the backside of the semiconductor waferformed with the circuit on the front surface, and performing the dicingof the wafer.

(11) The processing method of the semiconductor wafer as set forth inany one of (8) to (10) further comprising the step of applying orgenerating a heat.

Effect of the Invention

According to the present invention, in the adhesive sheet, the lowmolecular weight compound amount included in the adhesive agent beforeand after the curing by the energy ray is significantly reduced, hencethe various problems such as the compositional changes along with thevolatilization of the low molecular weight compound and the generationof the volatile gas or so can be solved. Furthermore, when using as forthe semiconductor wafer processing, though the water is sprayed in orderto remove the heat and the debris generated during the backside grindingand the dicing of the wafer, there is no composition change of theadhesive layer due to the flow out of the low molecular weight compound,since the amount of the low molecular weight compound included in theadhesive agent is significantly lowered.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the preferable embodiment of the present invention will bedescribed in detail including the embodiment of the best mode.

The energy ray-curable polymer (A) of the present invention is theenergy ray-curable polymer having the radical generation group capableof initiating the polymerization reaction under the excitation of theenergy ray and the energy ray polymerization group bonded to the mainchain or the side chain. As for the preferable embodiment, it isobtained by reacting the radical generating group containing polymer(a1) comprising the radical generating group containing monomer unit,the functional group containing monomer unit and other monomersdepending on the needs, and the energy ray-polymerizing group containingcompound (a2) comprising the substituent group reacting with saidfunctional group.

[The Radical Generating Group containing Monomer]

The radical generating group containing monomer used in the presentinvention becomes the monomer which derives the radical generating groupof the energy ray-curable polymer of the present invention. Said monomercomprises the polymerizable double bond, and the group generating thefree radical group (radical) which initiates the polymerization reactionunder the excitation by the energy ray. As for the radical generatinggroup, for example, the group including the phenyl carbonyl group whichmay comprise the substituent group in the aromatic ring; as shown in thefollowing general formula.

(R1 may be hydrogen atom or a carbohydrate group having carbon atoms of1 to 12, and ether bond and hydroxyl group my be present with in R1)

Such radical generating group containing monomer is for example obtainedby the addition reaction of the compound comprising the radicalgenerating group and the compound comprising the polymerizable doublebond.

As for the compound comprising the radical generating group, forexample, photo polymerization initiator comprising the hydroxyl groupmay be mentioned. Specifically,

may be mentioned.

The monomer obtained by the addition reaction of such compoundcomprising the radical generating group and the compound comprising thepolymerizable double bond, is preferable as the radical generating groupcontaining monomer.

As for the compound comprising the polymerizable double bond, thecompound comprising the polymerizble double bond having the functionalgroup which react with the hydroxyl group is preferable; and forexample, methacryloyloxyethyl isocyanate,meth-isopropenyl-α,α-dimethylbenzyl isocyanate, methacryloyl isocyanate,allyl isocyanate; glycidyl(meth)acrylate and; (meth)acrylic acid may bementioned. Also, acryloyl monoisocyanate compound obtained by reacting adiisocyanate or polyisocyanate compound with hydroxyethyl(meth)acrylate;and acryloyl monoisocyanate compound obtained by reaction ofdiisocyanate or polyisocyanate compound, a polyol compounds andhydroxyethyl(meth)acrylate may be mentioned.

By reacting said compound comprising the hydroxyl group and the radicalgenerating group, with said compound comprising the polymerizable doublebond (for example, methacryloyloxyethyl isocyanate); the hydroxyl groupof the compound comprising the radical generating group and thefunctional group (for example, isocyanate group) of the compoundcomprising the polymerizable double bond reacts; thereby the radicalgenerating group containing monomer having the polymerizable double bondcan be obtained.

As for the specific example of other monomers, o-acryloylbenzophenone,p-acryloylbenzophenone, o-methacryloylbenzophenone,p-methacryloylbenzophenone, p-(meth)acryloylethoxybenzophenone,monohydroxyalkylacrylate having 2 to 12 methylene groups derived fromthe benzophenone carbonic acid shown in the following general formula,or bezophenone carbonate ester of the monohydroxymethacrylate.

(R₁ and R₂ may be hydrogen atom or alkyl group having 1 to 4 of carbonatoms respectively, R₃ may be hydrogen or a methyl group and m is aninteger from 2 to 12), and compound in the following general formula,

(R₁ and R₂ may be hydrogen atom or alkyl group having 1 to 4 of carbonatoms respectively, and R₃ and R₄ includes hydrogen or methyl grouprespectively.) may be mentioned.(The Radical Generating Group containing Polymer(a1))

The radical generating group containing polymer (a1) is formed bypolymerizing the radical generating group containing monomer, thefunctional group containing monomer for introducing the energyray-polymerizable group, and other monomers if needed.

(The Functional Group containing Monomer)

The functional group containing monomer constituting the radicalgenerating group containing polymer (a1) is a monomer for introducingthe energy ray-polymerizable group to the energy ray-curable polymer ofthe present invention. It is a monomer comprising the polymerizabledouble bond, and the functional group, such as the hydroxyl group, thecarboxyl group, the amino group, the substituted amino group, the epoxygroup or so in the molecule, and preferably an unsaturated compoundcontaining the hydroxyl group or an unsaturated compound containing thecarboxyl group are used.

As specific examples of such functional group containing monomer, anacrylate containing hydroxyl group such as 2-hydroxyehtyl acrylate,2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropylmethacrylate, 2-hydroxybutyl acrylate and 2-hydroxybutyl methacrylate;and compounds containing carboxyl group such as acrylic acid,methacrylic acid, and itaconic acid or so, may be mentioned. The abovementioned functional group containing monomer may be used alone or incombination of two or more thereof.

[Other Monomers]

Other monomers constituting the radical generating group containingpolymer (a1) are not particularly limited, however, for example, as thepolymer, an acrylic copolymer mainly using the acrylic monomer, and theolefin copolymer mainly using the olefin monomer may be mentioned. Ifthe energy ray-curable polymer of the present invention is used as theadhesive agent, various acrylic copolymer which is relatively easy tocontrol the adhesive force is preferable, and various acrylic monomer isused as the constitution unit.

As for the acrylic monomer, an (meth)acrylic acid alkyl ester having 1to 18 carbon atoms of alkyl group is used. As the derivative of(meth)acrylic acid alkyl ester, methyl acrylate, metyl methacrylate,ethyl acrylate, ethyl methacrylate, propyl acrylate, propylmethacrylate, isopropyl acrylate, isopropyl methacrylate, n-butylacrylate, n-butyl methacrylate, isobutyl acrylate, isobutylmethacrylate, n-hexyl methacrylate, 2-ethyl hexyl acrylate, 2-ethylhexylmethacrylate, cyclohexyl acrylate, lauryl methacrylate, dimethylacrylamide or so may be mentioned.

Furthermore, a vinyl monomer copolymerizable with the above mentionedester monomer may be copolymerized. As for the copolymerizable vinylmonomer, styrene, α-methyl styrene, vinyl toluene, vinyl formate, vinylacetate, acrylonitrile, glycidyl acrylate, glycidyl methacrylate or somay be mentioned.

(The Formation of the Radical Generating Group containing Polymer (a1))

The radical generating group containing polymer (a1) is formed bypolymerizing the above mentioned radical generating group containingmonomer, the functional group containing monomer, and other monomers ifneed.

The radical generating group containing polymer (a1) contains thestructural units derived from the above radical generating groupcontaining monomer usually in an ratio of 0.1 to 30 weight %, preferably0.5 to 10 weight %, and more preferably 1 to 5 weight %. The radicalgenerating group containing polymer (a1) contains the structural unitsderived from the above functional group containing monomer usually in anratio of 1 to 70 weight %, preferably 5 to 40 weight %, and morepreferably 10 to 30 weight %. The radical generating group containingpolymer (a1) contains the structural units derived from above othermonomers usually in an ratio of 0 to 99 weight %, preferably 35 to 90weight %, and more preferably 50 to 80 weight %.

The radical generating group containing polymer (a1) is obtained bycopolymerizing the above mentioned radical generating group containingmonomer, the functional group containing monomer, and other monomers bya usual method; however, the production method of the radical generatinggroup containing polymer (a1) is not particularly limited, and forexample, it may be produced by using the solution polymerization underthe presence of the solvent, the chain transfer agent, and thepolymerization initiator or so; or by the aqueous emulsionpolymerization under the presence of the emulsifier, the chain transferagent, the polymerization initiator, and the dispersing agent, or so.

Note that, the monomer concentration during the polymerization isusually 30 to 70 weight %, preferably 40 to 60 weight % or so. As forthe polymerization initiator used for the polymerization, a persulfatesuch as potassium persulfate, ammonium persulfate or so, an azo compoundsuch as 2,2-‘azobisisobutylonitrile,2,2′-azobis(2,4-dimethylvaleronitrile) or so, called an peroxide such ashydrogen peroxide, benzoyl peroxide, lauryl peroxide or so, and a redoxpolymerization initiator comprising the combination of ammoniumpersulfate, with sodium sulfite or acid sodium sulfite or so may bementioned. The amount of the polymerization initiator mentioned in theabove is controlled within the range of 0.2 to 2 weight %, andpreferably within the range of 0.3 to 1 weight % with respect to thewhole amount of the monomer used in the polymerization.

Further, as for the chain transfer agent added during thecopolymerization; alkyl mercaptans such as octyl mercaptan, nonylmercaptan, decyl mercaptan, dodecyl mercaptan or so; thioglycolates suchas octyl thioglycolate, nonyl thioglycolate, 2-ethyl hexylthioglycolate, 2-ethyl hexyl β-mercaptopropionate or so;2,4-diphenyl-4-methyl-1-pentene, 1-methyl-4-isopropylidine-1-cyclohexeneor so may be mentioned. Particularly, when using the thioglycolates,2,4-diphenyl-4-methyl-1-pentene, and1-methyl-4-isopropylidine-1-cyclohexene, it is preferable since theobtained copolymer has low odor. Note that, the amount of chain transferagent is controlled within the range of 0.001 to 3 weight % or so withrespect to the whole monomer to be polymerized. Also, usually, thepolymerization reaction is performed under 60 to 100° C. for 2 to 8hours. Further, a viscosity improver, a wetting agent, a leveling agent,and an anti-foaming agent may be added accordingly.

[The Energy Ray-Curable Polymer (A)]

The energy ray-curable polymer (A) of the present invention is obtainedby reacting the functional group derived from the functional groupcontaining monomer of above mentioned radical generating groupcontaining polymer (a1) with the energy ray-polymerizable groupcontaining compound (a2).

[The Energy Ray-Polymerizable Group containing Compound (a2)]

The energy ray-polymerizable group containing compound (a2) includes,the substituent group which can react with the functional group. Thissubstituent group varies depending on the type of said functional group.For example, when the functional group is a hydroxyl or carboxyl group,the substituent group is preferably an isocyanate or epoxy group. Whenthe functional group is a carboxyl group, then the substituent group ispreferably an isocyanate or epoxy group. When the functional group is anamino or a substituted amino group, the substituent group is preferablyan isocyanate or the like. When the functional group is epoxy group, thesubstituent group is preferred to be a carboxyl group. One substituentgroup is contained in every molecule of the energy ray-polymerizablegroup containing compound (a2).

Further, 1 to 5, and preferably 1 to 2 carbon-carbon double bond of theenergy ray-polymerizable group, is contained in the energyray-polymerizable group containing compound (a2). As specific examplesof the energy ray-polymerizable group containing compound (a2);methacryloyloxyethyl isocyanate, meth-isopropenyl-α, α-dimethylbenzylisocianate, methacryloyl isocyanate, allyl isocyanate,glycidyl(meth)acrylate and (meth)acrylic acid or so may be mentioned.Also, acryloyl monoisocyanate compound obtained by reaction of adiisocyanate or polyisocyanate compound with hydroxyethyl(meth)acrylate;acryloyl monoisocyanate compound obtained by reaction of a mixture of adiisocyanate or polyisocyanate compound, a polyol compound andhydroxyethyl(meth)acrylate may be mentioned as well.

As for the energy ray-polymerizable group containing compound (a2), anenergy ray-polymerizable group containing polyalkyleneoxy compound, asdescribed in the following, can be used as well.

In the above formula, R¹ is hydrogen atom or methyl group, andpreferably methyl group. R² to R⁵ are each independently hydrogen oralkyl group having 1 to 4 carbon atoms, and preferably hydrogen.Further, n is an integer of 2 or higher, and preferably 2 to 4. That is,since n is 2 or higher, in the above energy ray-polymerizable groupcontaining polyalkyleneoxy compound includes 2 or more R². In here, R²which exists 2 or more, may be same or different from each other. Thiscan be said to R³ to R⁵ as well. NCO in the chemical formula 5 indicatesisocyanate group.

[Synthesis of the Energy Ray-Curable Polymer (A)]

The energy ray-curable polymer (A) of the present invention is obtainedby reacting the radical generating group containing polymer (a1) and theenergy ray-polymerizable group containing compound (a2) having asubstituent group which reacts with the functional group of said radicalgenerating group containing polymer (a1). Hereinafter, the productionmethod of the energy ray-curable polymer (A) of the present inventionwill be described, particularly the example of using the acryliccopolymer as a main skelton will be described. However, the energyray-curable polymer (A) of the present invention is not limited to thoseobtained by the method of production described hereinafter.

When manufacturing the energy ray-curable polymer (A), the energyray-polymerizable group containing compound (a2) is used in an amount of100 to 5 equivalent amounts, preferably 70 to 10 equivalent amounts, andmore preferably 40 to 15 equivalent amounts, per 100 equivalent amountsof the functional group containing monomer of the radical generatinggroup containing polymer (a1).

The reaction between the radical generating group containing polymer(a1) and the energy ray-polymerizable group containing compound (a2) isusually performed at room temperature and at atmospheric pressure for 24hours. It is preferable that this reaction is carried out in a solution,for example, an ethyl acetate solution in the presence of a catalystsuch as dibutyltin laurate.

As a result, the functional group present in the side chain of theradical generating group containing polymer (a1) and the substituentgroup in the energy ray-polymerizable group containing compound (a2)reacts, and the energy ray-polymerizable group is introduced into theradical generating group (a1); thereby the acrylic energy ray-curablepolymer (A) is obtained. In this reaction the reactivity between thefunctional group and the substituent group is usually 70% or more,preferably 80% or more, and it is preferable that the non reactingfunctional group does not remain in the energy ray-curable polymer (A).

When using the energy ray-polymerizable group containing polyalkyleneoxycompound, the acrylic energy ray-curable polymer (A) binding the energyray-polymerizable group via the polyalkyleneoxy compound is obtained.

The weight average molecular weight of the energy ray-curable polymer(A) bonded with the energy ray-polymerizable group and the radicalgenerating group is preferably 300,000 to 1,600,000, and furtherpreferably 400,000 to 900,000. Also, usually 1×10²¹ to 1×10²⁴,preferably 5×10²¹ to 8×10²³, and more preferably 1×10²² to 5×10²³ ofpolymerizable groups are contained per 100 g of the energy ray-curablepolymer (A). Further, usually 1×10²⁰ to 1×10²⁴, preferably 2×10²⁰ to5×10²³, and more preferably 5×10²⁰ to 2×10²³ of the radical generatinggroups are contained per 100 g of the energy ray-curable polymer (A).

[The Energy Ray-Curable Adhesive Composition]

The adhesive composition of the energy ray-curable type is obtained byblending the appropriate additives depending on the needs to the energyray-curable polymer of the present invention.

As the additives, for example, the crosslinkers (B), tackifier, pigment,dye, filler or so may be mentioned; however, the adhesive compositionmay be the energy ray-curable polymer alone and without the blendingthereof.

[The Crosslinkers (B)]

As for the crosslinkers (B), for example, an organic polyvalentisocyanate compound, an organic polyvalent epoxy compound and an organicpolyvalent imine compound or so may be mentioned.

As for the above mentioned organic polyvalent isocyanate compound, anaromatic polyvalent isocyanate compound, an aliphatic polyvalentisocyanate, and an alicyclic polyvalent isocyanate compound may bementioned. As for further specific examples of the organic polyvalentisocyanate compound; 2,4-tolylene diisocyanate, 2,6-tolylenediisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate,diphenylmethane-4,4′-diisocyanate, diphenylmethane-2,4′-diisocyanate,3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate,isophorone diisocyanate, dicyclohexylmethane-4,4′-diisocyanate,dicyclohexylmethane-2,4′-diisocyanate, and lysine isocyanate or so maybe mentioned. A trimer of these polyvalent isocyanate compounds or anisocyanate terminated urethane prepolymer obtained by reacting thesepolyvalent isocyanate compounds with a polyol compound may be used aswell.

As for specific examples of the above organic polyvalent epoxy compound,for example, a bisphenol A epoxy compound, a bisphenol F epoxy compound,1,3-bis(N,N-diglycidylaminomethyl)benzene,1,3-bis(N,N-diglycidylaminomethyl)toluene,N,N,N′N′-tetraglycidyl-4,4-diaminodiphenylmethane or so may bementioned.

As specific examples of the above organic polyvalent imine compound, aN,N′-diphenylmethane-4,4′-bis(1-azridinecarboxyamide),trimethylolpropane-tri-β-aziridinyl propionate,tetramethylolmethane-tri-β-aziridinyl propionateN,N′-toluene-2,4-bis(1-aziridinecarboxyaminde)triethylenemelamine or somay be mentioned.

[The Formation of the Energy Ray-Curable Adhesive Composition]

The used amount of above mentioned crosslinkers (B) is preferably 0.01to 20 parts by weight and particularly preferably 0.1 to 10 parts byweight, with respect to 100 parts by weight of the energy ray-curablepolymer (A).

As for the energy ray-curable adhesive composition formed as such, thereis no need to further add the photo polymerization initiator or the lowmolecular weight compound such as the energy ray-polymerizable compoundto the energy ray-curable polymer (A), since the energy ray-curablepolymer (A) its self comprises the function as the photo polymerizationinitiator and the function as the energy ray polymerization compound.Therefore, according to the energy ray-curable adhesive composition ofthe present invention, the amount of the low molecular weight includedin the adhesive composition is significantly reduced, thus can solvevarious problems such as the compositional change along with thevolatilization of the low molecular weight, and the generation of thevolatile gas or so.

However, the photo polymerization initiator, the energyray-polymerizable low molecular weight compound, pigment, dye, filler orso may be included in said adhesive agent as far as it does notcompromise the object of the present invention. Among these, the lowmolecular weight compound having a molecular weight of 1000 or less maybe included at a ratio of 3 weight % or less in the adhesive agent.

[The Adhesive Sheet]

The adhesive sheet of the present invention is obtained by adhering theadhesive layer obtained from the adhesive composition of the presentinvention to the substrate. Also, depending on the needs, the releasefilm may be used in order to protect the adhesive layer.

[The Substrate]

The substrate used in the adhesive sheet of the present invention is notparticularly limited, and a polyethylene film, a polypropylene film, apolybutene film, a polybutadiene film, a polymethylpentene film, apolyvinyl chloride film, a vinyl chloride copolymer film, a polyethyleneterephthalate film, a polybutylene terephthalate film, a polyurethanefilm, an ethylene/vinyl acetate copolymer film, an ionomer resin film,an ethylene/(meth)acrylic acid copolymer film, an ethylene/(meth)acrylicacid ester copolymer film, a polystyrene film, a polycarbonate film, afluoro resin film, a low density polyethylene (LDPE) film, a linear lowdensity polyethylene (LLDPE) film, or hydrogenated and modified filmthereof may be used. Also, the crosslinking film thereof may be used aswell. The above mentioned substrate may be alone, or it may be acomposite film combining two or more thereof.

The thickness of the substrate varies depending on the use, however, itis usually 20 to 500 μm, and preferably 50 to 300 μm or so.

For example as described hereinafter, when the ultraviolet ray is usedas the energy ray applied to cure the adhesive, among the abovementioned substrates, the one which is transparent to the ultravioletray is preferable. Also, when the electron beam is used as the energyray, the substrates do not have to be transparent; hence addition to thefilms mentioned in the above, the opaque film by coloring them may beused.

[The Release Film]

As the release film, various films having the surface of a releaseproperty are used. As specific examples of such release film, apolyethylene film, a polypropylene film, a polybutene film, apolybutadiene film, a polymethylpentene film, a polyvinyl chloride film,a vinyl chloride copolymer film, a polyethylene terephthalate film, apolybutylene terephthalate film, a polyurethane film, an ethylene/vinylacetate film, an ionomer resin film, an ethylene/(meth)acrylic acidcopolymer film, an ethylene/(meth)acrylic acid ester copolymer film, apolystyrene film, a polycarbonate film, a fluorocarbon resin film, a lowdensity polyethylene (LDPE) film, a linear low density polyethylene(LLDPE) film, and hydrogenated and modified substrate thereof may beused. Also, the crosslinking film thereof may be used as well. The abovementioned film may be alone, or it may be a composite film combining twoor more thereof.

As the release film, the film in which the release treatment isperformed on to the one of the surface of above mentioned film ispreferable. A release agent used for the release treatment is notparticularly limited; however, a silicone type, a fluorine type, analkyd type, an unsaturated polyester type, a polyolefin type, a wax typeor so may be used. Particularly, the silicone release agent ispreferable since it can attain low releasing force. If the film used asthe release film has weak surface tension by itself, and has lowreleasing force to the adhesive layer, such as the polyolefin film, thenthere is no need for the release treatment.

As the method of the release treatment, the release agent is coatedusing a gravure coater, a meyer-bar coater, an air knife coater, or aroll coater or so to said film without the solvent, or by solventdiluting or emulsifying. Then, the release agent is heated, orirradiated with the ultraviolet ray or the electron beam for curing,thereby the release layer is formed.

The thickness of the above release film is preferably 12 μm or thicker,more preferably 15 to 1000 μm, and particularly preferably 50 to 200 μm.When the release film is too thin, the dimensional stability of theadhesive sheet itself becomes insufficient, against the stressaccumulating during the steps of stacking each layer constituting theadhesive sheet and the step of winding the adhesive sheet. If therelease layer is too thick, the whole thickness of the adhesive sheetbecomes too thick, hence it becomes difficult to handle.

[The Manufacturing of the Adhesive Sheet]

The adhesive sheet of the present invention comprises the abovementioned energy ray-curable adhesive composition and the substrate. Theadhesive sheet of the present invention is obtained by coating theenergy ray-curable adhesive agent with the appropriate thickness onvarious substrates in accordance with the generally known methods suchas a roll knife coater, a comma coater, a gravure coater, a die coater,a reverse coater or so; then the adhesive layer is formed by drying,followed by superimposing the release film on the adhesive layerdepending on the needs. Also, the adhesive sheet may be manufactured byproviding the adhesive layer on the release film and transferring theseonto said substrate.

The thickness of the adhesive layer varies depending on the use; howeverit is usually 5 to 100 μm, and preferably 10 to 40 μm or so. If theadhesive layer becomes thin, the adhesive property and the surfaceprotection function may decline.

The adhesive sheet of the present invention can lower the adhesive forceby the energy ray irradiation, and as for the energy ray, specificallythe ultraviolet ray and the electron beam or so are used. Also theirradiation amount varies depending on the type of the energy ray, andfor example when using the ultraviolet ray, the ultraviolet rayintensity is 50 to 300 mW/cm² or so, and the ultraviolet ray irradiationamount is preferably 100 to 1200 mJ/cm² or so.

The energy ray-curable adhesive layer used in the present invention hassufficient adhesive force before the energy ray irradiation; hence thesemiconductor wafer can be securely held during the semiconductor waferprocessing step such as backside grinding and dicing or so.

Said energy ray-curable adhesive layer cures by the energy rayirradiation and the adhesive force significantly declines. For example,the adhesive force against the mirror surface of the semiconductor waferis preferably 2000 to 15000 mN/25 mm and further preferably 5000 to10000 mN/25 mm or so before the energy ray irradiation, on the otherhand after the irradiation, it is 1 to 50% or so of that of before theirradiation.

[The Processing Method of the Semiconductor Wafer]

The adhesive sheet of the present invention can be used for processingthe semiconductor wafer as described in the following.

(The Wafer Backside Grinding Method)

During the backside grinding of the wafer, the wafer processing adhesivesheet is stuck to the circuit face of the semiconductor wafer formedwith the circuit on the front surface in order to protect the circuitsurface while the backside grinding of the wafer and to have apredetermined thickness of the wafer.

The semiconductor wafer can be a silicon wafer, or a compoundsemiconductor wafer such as gallium arsenide. The formation of thecircuit on the wafer surface can be performed by conventionally widelyused various methods such as an etching method and a lift off method orso. The predetermined circuit is formed during the circuit forming stepof the semiconductor wafer. The thickness of such wafer at before thegrinding is not particularly limited; however it is usually 500 to 1000μm or so.

Then, during the backside grinding, the adhesive sheet of the presentinvention is stuck to the circuit surface in order to protect thecircuit surface. The backside grinding is performed by known methodsusing the grinder and the vacuum table or so for fixing the wafer whilethe adhesive sheet is stuck. After the backside grinding step, thetreatment to remove the fractured layer due to the grinding may beperformed.

After the backside grinding step, the energy ray is irradiated to theadhesive sheet to cure the adhesive agent for reducing the adhesiveforce, then the adhesive sheet is released from the circuit surface. Theadhesive sheet of the present invention has sufficient adhesive forcebefore the energy ray irradiation; hence the wafer is securely heldduring the backside grinding of the wafer, and also can prevent thepenetration of the grinding water into the circuit surface. Also, theadhesive force declines significantly after the adhesive agent is curedby the energy ray irradiation; hence it can be easily released from thecircuit surface and the glue residue to the circuit surface can bereduced.

Further, according to the energy ray-curable adhesive agent of thepresent invention, the amount of the low molecular weight compoundincluded in the adhesive agent is significantly lowered; hence there isno flow out of the low molecular weight due to the grinding water.

(The Wafer Backside Processing Method)

Also, followed by said backside grinding step, various processing areperformed to the backside of the wafer.

For example, in order to further form the circuit pattern to thebackside of the wafer, the treatment involving the heat generation suchas an etching treatment or so may be performed. Also, the die bond filmmay be heat pressed to the backside of the wafer. During these steps,the circuit pattern can also be protected by adhering the adhesive sheetof the present invention; and, it will be exposed to a high temperaturecondition. However, since the low molecular weight compounds is notsubstantially included in the adhesive layer of the adhesive sheet ofthe present invention, the volatilization of the low molecular weightcompounds by heat generation and heat application during the processingcan be suppressed.

(The Wafer Dicing Method)

The adhesive sheet of the present invention has the property whichsignificantly reduces the adhesive force by the energy ray irradiation,hence it may be used as the dicing sheet.

When using as the dicing sheet, the adhesive sheet of the presentinvention is stuck to the backside of the wafer. The dicing sheet isstuck generally by the apparatus called a mounter, however it is notparticularly limited.

The dicing method of the semiconductor wafer is not particularlylimited. As for an example, the method of forming chips from a wafer byknown methods such as a method using a rotating round blade of a diceror so after fixing the peripheral portion of the dicing tape by the ringflame when dicing the wafer may be mentioned. Alternatively, it may be adicing method using a laser light. According to the adhesive sheet ofthe present invention, the amount of the low molecular weight compoundsincluded in the adhesive layer can be significantly reduced; hence thelow molecular weight compounds does not flow out due to the grindingwater.

Next, the energy ray is irradiated to the adhesive sheet and theadhesive agent is cured to reduce the adhesive force, then the chips arepicked up from the adhesive sheet. The chips picked up are then diebonded by usual method and resin sealed thereby the semiconductorapparatus is manufactured. According to the adhesive sheet of thepresent invention, the glue residue and the contamination due to the lowmolecular weight compound to the backside of the chips are reduced;hence no adverse effect due to the residue of the chip backside occurs.

Hereinabove, the energy ray-curable polymer of the present invention,particularly when using as the main component of the adhesive layer inthe wafer processing adhesive sheet was explained as an example, howeverthe energy ray-curable polymer of the present invention may be usedbesides the above mentioned, and for example it may be used as themolding resin, adhesive bond, paint and ink or so which has a adverseeffect due to the volatilization component.

EXAMPLE

Hereinafter the present invention will be described based on theexamples; however the present invention is not limited thereto.

Example 1

(Synthesis of the Radical Generating Group containing Monomer)

The radical generating group containing monomer was obtained by mixingand reacting,1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one (madeby Ciba speciality chemical Inc., product name “IRGACURE 2959”) andmethacryloyloxyethyl isocyanate at the same molar ratio.

(Synthesis of the Radical Generating Group containing Polymer)

The acrylic radical generating group containing polymer was synthesizedby a solution polymerization in ethyl acetate solution using; 57 partsby weight of butyl acrylate, 10 parts by weight of methylmethacrylate,28 parts by weight of 2-hydroxyethylacrylate as the functional groupcontaining monomer, and 5 parts by weight of the radical generatinggroup containing polymerizable monomer formed in the above.2,2-‘azobisisobutylonitrile was used as the polymerization initiator,and 2,4-diphenyl-4-methyl-1-pentene was used as the chain transferagent. (Hereinafter, if not particularly mentioned, the above mentionedpolymerization initiator and the chain transfer agent during thesynthesis of the radical generating group containing polymerizablecopolymer are used).

(Formation of the Energy Ray-Curable Polymer)

100 parts by weight, in terms of the solid portion, of this acrylicradical generating group containing polymer and 30 parts by weight ofmethacryloyloxyethyl isocyanate (80 equivalent amounts with respect to100 equivalent amounts of the hydroxyl group as a functional group ofthe acrylic radical generating group containing polymer) were reactedand obtained ethyl acetate solution (30% solution) of the acrylic energyray-curable polymer having weight average molecular weight of 630,000formed by bonding the polymerization group and radical generating group.

(Formation of the Energy Ray-Curable Adhesive Composition)

With respect to 100 parts by weight of this acrylic energy ray-curablepolymer, 0.625 parts (solid portion) by weight of the polyvalentisocyanate compound (made by Nippon Polyurethance Co., product name“Coronate L”) were mixed to obtain the acrylic energy ray-curableadhesive composition.

(Formation of the Adhesive Sheet)

The above mentioned adhesive composition was coated, so that thethickness of the coat is 40 μm after the drying, by using the roll knifecoater to the surface of the polyethylene telephtalate film (thicknessof 38 μm) which is silicone release treated as the release sheet. Next,after drying at 100° C. and 120° C. for 2 minutes, then polyethylenefilm having thickness of 110 μm as the substrate was stacked to theobtained adhesive layer, thereby the adhesive sheet was obtained. Inorder to stabilize the adhesive force, it was left under the atmosphereof 23° C.50% RH for 7 days, and then the following physical property andthe ability were evaluated.

“The Adhesive Force”

The adhesive force of the obtained adhesive sheet was measured asfollows.

The adhesive force of the adhesive sheet was measured by using UniversalTesting Instruments (TENSILON/UTM-4-100, made by ORIENTEC CO., LTD) atthe releasing speed of 300 mm/min, and releasing angle of 180° followingJIS Z0237, besides the mirror surface of the silicon wafer was theadherend, and the adhesive force before curing was determined.

Also, after the adhesive sheet was stuck to the mirror surface of thesilicon wafer, it was left under the atmosphere of 23° C.50% RH for 20minutes, and the ultraviolet ray irradiation was performed (irradiationcondition: intensity 350 mW/cm², amount of light 200 mJ/cm²) from thesubstrate side of the adhesive sheet by using the ultravioletirradiation apparatus (made by LINTEC Corporation, product name“RAD-2000”). The adhesive force was measured as similar as the above inregards with the adhesive sheet after the ultraviolet ray irradiation,and the adhesive force after the energy ray irradiation was determined.

“The Surface Contamination Property”

The surface contamination property when using the above mentionedadhesive sheet as the surface protection sheet during the backsidegrinding of the semiconductor wafer was evaluated as the following.

The above mentioned adhesive sheet was stuck to the patterned surface ofthe silicon dummy wafer (thickness: 725 μm, surface status: comprisesthe circuit pattern having 20 μm step difference at maximum), by usingthe tape laminator (made by LINTEC Corporation, product name“RAD-3510”). Then, by using the wafer backside grinding apparatus (madeby Disco Corporation, product name “DGP-8760”), the wafer thickness wasground till it becomes 100 μm thick. Next, the ultraviolet rayirradiation was performed (irradiation condition: intensity 350 mW/cm²,amount of light 200 mJ/cm²) by using the ultraviolet irradiationapparatus (made by LINTEC Corporation, product name “RAD-2000”) from thesubstrate of the adhesive sheet. Next, by using the tape mounter (madeby LINTEC Corporation, product name “RAD-2000F/12”), the dicing tape(made by LINTEC Corporation, product name “D-185”) was stuck to thegrinding surface, then said adhesive sheet was released from the circuitsurface.

Next, the circuit surface of the silicon dummy wafer was observed usingthe digital microscope (made by KEYENCE CORPORATION, product name“Digital microscope VHX-200”) at 2000 magnification. When the adhesiveresidual was not found, the surface contamination property was evaluated“good”, and when the residual was found, the surface contaminationproperty was evaluated “bad”.

“The Weight Reduction Rate (The Volatile Gas Amount) after Heating”

The weight reduction rate after heating was evaluated by measuring theweight reduction using the differential thermal•thermalgravitysimultaneous instrument (made by SHIMADZU CORPORATION, product name“DTG-60”). A piece of the above mentioned adhesive sheet (0.01 g;release film was removed) was raised up to 120° C. at 10° C./min,followed by heating at 120° C. for 60 minutes, then returned to roomtemperature and determined the weight reduction rate of before and afterthe heating.

Example 2

The acrylic radical generating group containing polymer was synthesizedby solution polymerizing in ethyl acetate solution, using 68.2 parts byweight of butyl acrylate, 10 parts by weight of methyl methacrylate,16.8 parts by weight of 2-hydroxyethylacrylate, and 5 parts by weight ofthe radical generating group containing monomer prepared in theexample 1. 100 parts by weight, in terms of the solid portion, of thisradical generating group containing polymer and 18.7 parts by weightmethacryloyloxyethyl isocyanate (83.3 equivalent amount with respect to100 equivalent amount hydroxyl group as a functional group of theacrylic radical generating group containing polymer) were reacted, andobtained ethyl acetate solution (30% solution) of the energy ray-curablepolymer having a weight average molecular weight of 680,000 formed bybonding the polymerization group and radical generating group.

With respect to 100 parts by weight of this energy ray-curable polymer,0.625 parts by weight (solid portion) of the polyvalent isocyanatecompound (made by Nippon Polyurethance Co., product name “Coronate L”)were mixed to obtain the energy ray-curable adhesive composition.

The same procedures were performed as the example 1 except for formingthe adhesive layer by using the above mentioned adhesive composition.The results are shown in Table 1.

Example 3

The acrylic radical generating group containing polymer was synthesizedby solution polymerizing in ethyl acetate solution using, 68.2 parts byweight of butyl acrylate, 10 parts by weight of methyl methacrylate,16.8 parts by weight of 2-hydroxyethylacrylate, and 1 parts by weight ofthe radical generating group containing monomer prepared in theexample 1. 100 parts by weight, in terms of the solid portion, of thisradical generating group containing polymer and 18.7 parts by weight ofmethacryloyloxyethyl isocyanate (83.3 equivalent amount with respect to100 equivalent amount hydroxyl group as a functional group of theacrylic radical generating group containing polymer) were reacted, andobtained ethyl acetate solution (30% solution) of the energy ray-curablepolymer having weight average molecular weight of 680,000 formed bybonding the polymerization group and radical generating group.

With respect to 100 parts by weight of this energy ray-curable polymer,0.625 parts by weight (solid portion) of the polyvalent isocyanatecompound (made by Nippon Polyurethance Co., product name “Coronate L”)were mixed to obtain the energy ray-curable adhesive composition.

The same procedures were performed as the example 1 except for formingthe adhesive layer by using the above mentioned adhesive composition.The results are shown in Table 1.

Comparative Example 1 (Formation of the Adhesive Composition)

The acrylic copolymer was synthesized by solution polymerizing in ethylacetate solution using, 62 parts by weight of butyl acrylate, 10 partsby weight of methyl methacrylate, and 28 parts by weight of2-hydroxyethylacrylate. 100 parts by weight, in terms of the solidportion, of this acrylic copolymer and 30 parts by weight ofmethacryloyloxyethyl isocyanate (80 equivalent amount with respect to100 equivalent amount hydroxyl group as a functional group of theacrylic copolymer) were reacted, and obtained ethyl acetate solution(30% solution) of the acrylic copolymer having weight average molecularweight of 600,000 formed by bonding the polymerizable group via analkylene oxide group.

With respect to 100 parts by weight of this acrylic copolymer, 0.625parts by weight (solid portion) of the polyvalent isocyanate compound(made by Nippon Polyurethance Co., product name Coronate L), and 3.3parts by weight (solid portion) of the photopolymerization initiator(made by Ciba speciality chemical Inc., product name IRGACURE 184) weremixed and obtained the adhesive composition.

The same procedures were performed as the example 2 except for formingthe adhesive layer by using the above mentioned adhesive composition.The results are shown in Table 1.

Comparative Example 2

The acrylic copolymer was synthesized by solution polymerizing in ethylacetate solution using, 73.2 parts by weight of butyl acrylate, 10 partsby weight of methyl methacrylate, and 16.8 parts by weight of2-hydroxyethylacrylate. 100 parts by weight, in terms of the solidportion, of this acrylic copolymer and 18.7 parts by weight ofmethacryloyloxyethyl isocyanate (83.3 equivalent amount with respect to100 equivalent amount hydroxyl group as a functional group of theacrylic copolymer) were reacted, and obtained ethyl acetate solution(30% solution) of the acrylic adhesive polymer having weight averagemolecular weight of 600,000 formed by bonding the polymerization groupvia the alkylene oxide group.

With respect to 100 parts by weight of this acrylic adhesive polymer,0.625 parts by weight (solid portion) of the polyvalent isocyanatecompound (made by Nippon Polyurethance Co., product name Coronate L),and 3.3 parts by weight (solid portion) of the photopolymerizationinitiator (made by Ciba speciality chemical Inc., product name IRGACURE184) were mixed and obtained the adhesive composition.

The same procedures were performed as the example 2 except for formingthe adhesive layer by using the above mentioned adhesive composition.The results are shown in Table 1.

Comparative Example 3

The acrylic copolymer having weight average molecular weight of 600,000was synthesized by solution polymerizing in ethyl acetate solutionusing, 73.2 parts by weight of butyl acrylate, 10 parts by weight ofmethyl methacrylate, and 16.8 parts by weight of 2-hydroxyethylacrylate.100 parts by weight, in terms of the solid portion, of this acryliccopolymer and 18.7 parts by weight of methacryloyloxyethyl isocyanate(83.3 equivalent amount with respect to 100 equivalent amount hydroxylgroup as a functional group of the acrylic copolymer) were reacted, andobtained ethyl acetate solution (30% solution) of the acrylic adhesivepolymer formed by bonding the polymerization group via the alkyleneoxide group.

With respect to 100 parts by weight of this acrylic adhesive polymer,0.625 parts by weight (solid portion) of the polyvalent isocyanatecompound (made by Nippon Polyurethance Co., product name Coronate L),and 3.3 parts by weight (solid portion) of the photopolymerizationinitiator (made by Ciba speciality chemical Inc., product name IRGACURE184) were mixed and obtained the adhesive composition.

The same procedures were performed as the example 2 except for formingthe adhesive layer by using the above mentioned adhesive composition.The results are shown in Table 1.

TABLE 1 Surface The weight reduction Adhesive force mN/25 mm)Contamination rate after heating (The Adhesive Layer Adhesive LayerProperty out gas amount) (%) 100° C. during 120° C. during 100° C. 120°C. 100° C. 120° C. the drying the drying during during during duringBefore After Before After the the the the curing curing curing curingdrying drying drying drying Example 1 9300 230 9000 240 Good Good −1.09−1.10 Example 2 12000 280 11500 290 Good Good −1.04 −1.03 Example 3 8000400 8300 420 Good Good −1.06 −1.06 Comparative 9200 280 9900 800 GoodBad −5.15 −4.21 example 1 Comparative 13100 320 12300 950 Good Bad −5.21−4.32 example 2 Comparative 12100 350 11000 1150 Good Bad −5.18 −4.23example 3

1. An energy ray-curable acrylic polymer having a radical generatinggroup capable of initiating polymerization reaction under the excitationby an energy ray, and an energy ray-polymerizable group bonded to a mainchain or a side chain of the polymer.
 2. The energy ray-curable acrylicpolymer as set forth in claim 1 wherein said radical generating groupincludes a phenyl carbonyl group which may comprise a substituent groupin an aromatic ring.
 3. The energy ray-curable acrylic polymer as setforth in claim 2 wherein said radical generating group is derived from amonomer obtained by adding a compound comprising a polymerizable doublebond to a hydroxyl group of a photo polymerization initiator comprisinghydroxyl group.
 4. The energy ray-curable acrylic polymer as set forthclaim 3 having a weight average molecular weight of 300,000 to1,600,000.
 5. An energy ray-curable adhesive composition comprising theenergy ray-curable acrylic polymer as set forth in claim
 4. 6. Anadhesive sheet comprising a substrate and an energy ray-curable adhesivelayer formed thereon, and said energy ray-curable adhesive layercomprising the energy ray-curable adhesive composition as set forth inclaim
 5. 7. The adhesive sheet as set forth in claim 6 used for asemiconductor wafer processing.
 8. A processing method of asemiconductor wafer comprising the step of adhering the energyray-curable adhesive layer of the adhesive sheet as set forth in claim 7to a circuit surface of the semiconductor wafer formed with the circuiton the front surface, and performing the backside processing of thewafer.
 9. The processing method of the semiconductor wafer as set forthin claim 8 wherein said backside processing of the semiconductor waferis the backside grinding.
 10. The processing method of the semiconductorwafer comprising the step of adhering the energy ray-curable adhesivelayer of the adhesive sheet as set forth in claim 7 to the backside ofthe semiconductor wafer formed with the circuit on the front surface,and performing dicing of the wafer.
 11. The processing method of thesemiconductor wafer as set forth in claim 10 further comprising the stepinvolving a heat application or a heat generation.
 12. An energyray-curable adhesive composition comprising: an energy ray-curablepolymer having a radical generating group capable of initiatingpolymerization reaction under the excitation by an energy ray, and anenergy ray-polymerizable group bonded to a main chain or a side chain ofthe polymer.
 13. The energy ray-curable adhesive composition as setforth in claim 12 wherein said radical generating group includes aphenyl carbonyl group which may comprise a substituent group in anaromatic ring.
 14. The energy ray-curable adhesive composition as setforth in claim 13 wherein said radical generating group is derived froma monomer obtained by adding a compound comprising a polymerizabledouble bond to a hydroxyl group of a photo polymerization initiatorcomprising hydroxyl group.
 15. The energy ray-curable adhesivecomposition as set forth in claim 14 having a weight average molecularweight of 300,000 to 1,600,000.
 16. An adhesive sheet comprising asubstrate and an energy ray-curable adhesive layer formed thereoncomprising the energy ray-curable adhesive composition as set forth inclaim 12, wherein an adhesive force against a mirror surface of thesemiconductor wafer is 2000 to 1500 mN/25 mm before the energy rayirradiation and after the energy ray irradiation the adhesive force is 1to 50% of that before the irradiation.
 17. The adhesive sheet as setforth in claim 16 used for a semiconductor wafer processing.
 18. Aprocessing method of a semiconductor wafer comprising the step ofadhering the energy ray-curable adhesive layer of the adhesive sheet asset forth in claim 17 to a circuit surface of the semiconductor waferformed with the circuit on the front surface, and performing thebackside processing of the wafer.
 19. The processing method of thesemiconductor wafer as set forth in claim 18 wherein said backsideprocessing of the semiconductor wafer is the backside grinding.
 20. Theprocessing method of the semiconductor wafer comprising the step ofadhering the energy ray-curable adhesive layer of the adhesive sheet asset forth in claim 17 to the backside of the semiconductor wafer formedwith the circuit on the front surface, and performing dicing of thewafer.
 21. The processing method of the semiconductor wafer as set forthin claim 20 further comprising the step involving a heat application ora heat generation.